Wireless networks and systems are becoming increasingly popular. Wireless communications, however, are constrained due to a limited amount of available, interference free spectrum that may be used for reliable communications within a geographic area.
To enhance the availability and reliability of interference free spectrum, procedures that are governed by regulatory agencies (e.g., the Federal Communications Commission (FCC) in the United States) have been developed for allocating and governing spectrum use. In the U.S., for example, the FCC licenses spectrum in a primary spectrum market to Commission licensees. A secondary market exists for the Commission licensees to sublease spectrum for use by other parties. An entity that seeks to transfer spectrum in the secondary market commonly is referred to as a “spectrum provider” or a “spectrum holder,” and an entity or wireless communications system or device that has a need for spectrum to carry out wireless communications commonly is referred to as a “spectrum user.” A spectrum provider or holder also may be a spectrum user.
In the U.S., some spectrum may be used without a license, but regulations on the spectrum may be imposed. For example, the FCC has implemented the elimination of analog television (TV) broadcasts in favor of digital TV broadcasts. This has freed up spectrum channels for use by unlicensed radio systems to offer various services, such as mobile communications and Internet access. This freed spectrum is commonly referred to as TV whitespace (TVWS), which is made up of the guard bands and unused TV channels between channel 2 and channel 51 (corresponding to 54 MHz to 698 MHz).
To avoid interference with digital TV broadcasts and other incumbent systems, such as wireless microphone systems, radios that use the TV whitespace are required to register and receive a channel map of available channels that may be used for the communications activity of the radio system. Current regulations require these radio systems to register every twenty-four hours. Also, for mobile radios, if the radio moves into a new location, a new registration is required. Other regulations on the radios are present, such as transmitted power limits for different types of radios. Additional information regarding the regulation of TV whitespace may be found in FCC 08-260, Second Report and Order and Memorandum Opinion and Order, Adopted Nov. 4, 2008 and Released Nov. 14, 2008, the entirety of which is incorporated herein by reference. Similar proposals have been made in places other than the United States. For example, Ofcom in the United Kingdom has described access to certain spectrum by cognitive radios in “Digital Dividend: Cognitive—Access Consultation on License-Exempting Cognitive Devices Using Interleaved Spectrum,” published Feb. 16, 2009.
Conventional wireless networks use radios that transmit or receive communications within a fixed channel set or band. In some circumstances, radios are permitted to search among a predefined set of channels in a programmed way, as in trunked radio or cellular networks. The pool of available spectrum, however, is typically finite (or static), and radio channels and bandwidth are not optimized on an individual user or application basis. This leads to high inefficiencies in spectrum utilization, and since spectrum is a scarce resource, less than optimal performance for the user and network as a whole. To address such limitations, systems employing “cognitive networking” are being developed. Cognitive networking can be described as a method of wireless communication in which a network or a wireless node changes its transmission or reception parameters (e.g., the channel or bandwidth) to communicate, while avoiding interference with other users. This alteration of parameters is based on the active monitoring of several factors in the radio environment, such as user behavior and network conditions. In this manner, spectrum allocation is performed with an aim toward maximizing communication performance while minimizing interference among devices on the network.
A simple form of spectrum allocation is referred to in the art as direct spectrum allocation. Direct spectrum allocation is based upon a simple request for spectrum (in terms of frequency, location, and time for example). A specific implementation of this is the conventional allocation of TV white space. Requests are made directly by a radio (through an application programming interface (API) and via the internet) to a database controlled by a hosting entity that is a spectrum provider. The database and/or the radios conventionally are computer-implemented systems capable of storing software (programs, code, and/or logical instructions) and data on a computer readable medium (e.g., a memory), and capable of executing software for carrying out the software functions with a processor. In this manner, the database may include a channel allocation engine.
In simple direct spectrum allocation, allocations are made from a pool of available spectrum, for a specific location with no effort to avoid contention between radios or ensure hardware compatibility. In particular, an allocation engine resident in the host spectrum provider manages the spectrum database, and the allocation engine draws from the database and simply grants access to all available channels in accordance with a set of rules, such as those defined in the FCC's Second Report and Order and Memorandum Opinion and Order (FCC 08-260) on Unlicensed Operation in the TV Broadcast Bands. The grant is made in the form of a channel map provided by the allocation engine to the radio device. After a requesting radio receives a channel map of available spectrum, the final channel selection is made by the radio.
Direct spectrum allocation often is deficient because aside from spectrum availability, the channel map is not generated based on any parameters that relate to communication efficiency and interference issues. Accordingly, although a radio device may select any channel from the channel map, there is no guarantee that a selected channel will provide efficient, interference free use of the spectrum.
Direct spectrum allocation may be enhanced by implementing processes referred to in the art as “managed spectrum access”. Managed spectrum access generally attempts to address the need to minimize congestion and interference among devices, while optimizing the quality of service. This can be accomplished by increasing the channel to allocation engine's knowledge of a radio's operating environment. For example, the allocation engine may consider information pertaining to the density of users on each channel, possible sources of interference, usage patterns and radio feedback, and the like. Because the spectrum allocation engine knows the location of registered radios, the location of possible interferers, the availability of alternate channels, and may have some feedback from the radio on real-time local radio frequency (RF) conditions, a weighted or ranked set of available channels (in order of predicted quality of service or preference the wireless communications application of the radio) can be derived for each radio by assessing the overall environment in which a radio managed by the engine is operating.
Managed spectrum access can further be enhanced by providing exclusive use channels to managed radios. In some instances, a usage fee may be imposed for exclusive use. Exclusive use channels would be offered by entering them into the available spectrum pool. One source of exclusive use channels might be broadcasters or spectrum holders (e.g., spectrum licensees) seeking to “rent” unused capacity.
One major distinction between managed spectrum access and simple direct spectrum allocation is that spectrum allocations in the managed spectrum access model are intended to be made for a finite geographic area, on a non-interfering basis. Managed spectrum access, therefore, strives to achieve physical separation among radios that operate on interfering channels, thus minimizing or eliminating the possibility of RF interference.
To allocate spectrum efficiently and on a non-interfering basis, spectrum should be described in terms that render spectrum tantamount to a fungible asset. In this manner, “chunks” of spectrum can be used, transferred, and otherwise manipulated as a commoditized object or entity. Conventionally, spectrum has been allocated principally in terms of area, time, and frequency. FIG. 1 is a schematic graph of blocks of conventional spectrum use rights that may be transferred from a corresponding spectrum holder to a spectrum user. The components that identify a block of spectrum include a time window, a frequency-based spectral mask, a geographic coverage area, and/or a transmitted power limit, which may be combined to form a spectrum commodity object 10. The graph of FIG. 1 schematically illustrates blocks of spectrum in three dimensions, including time, space (or geographic coverage area) and frequency. Each spectrum commodity object 10 also may have the associated transmitted power limit, which is a power value that radios operating in accordance with the transmitted power limit may not exceed. Each spectrum commodity object 10 may be associated with use rights that may be transferred from a corresponding spectrum holder to a spectrum user in the secondary market. The spectrum commodity object may have an associated monetary or non-monetary value, or may not be associated with a value.
However, improvements may be made to the allocation of spectrum principally based on area, time, and frequency.